SUBCARBONIFEROUS PERIOD. 



319 



longispinus ; fig. 554, Spiriferglaber. Spirifer speciosus and Chonetes Dalmaniana 

 are common species. Pleurotomaria carinata retains its original colored markings, 

 as first observed by the late Professor Forbes; and this author hence inferred that 



Fi°;s. 553-555. 



Fig. 553, Productus longispinus ; 554,Sphifer glaber ; 555, Nautilus (Trematodiscus) Koninckii. 



it was a shallow-water species, as only such have shells figured with colors 

 Fig. 555, Nautilus {Trematodiscus) Koninckii. 



Trilobites occur of the only three Carboniferous genera, Phil- 

 lipsia, Grifjithides, and Bracliymetop>us. Fig. 556 is Phillipsia 

 seminifera. 



Remains of fishes are very common in Europe and Britain. 

 Among Cestracionts (or sharks with pavement-teeth) there are 

 Cochliodus contortus (fig. 547) ; among Hybodonts (or sharks 

 with regular teeth, the teeth with obtuse or rounded edges) there 

 is the Cladodus marginatus. Fig. 557 represents a small spe- 

 cimen of one of the great fish-spines of this period, called Cte- 

 nacanthus major by Agassiz. One specimen has a length of 

 fourteen and a half inches, and was probably eighteen inches in 

 the living Cestraciont. The old fishes, as Agassiz observes, must 

 have had gigantic dimensions, if we may judge from the size 

 of the spines. 



Fie;. 557. 



Phillipsia semi- 

 nifera. 



Part of a spine of Ctenacanthus major. 



Another spine, Oracanthus Milleri, Agassiz, is nine and a half inches long and 

 three inches wide at base, and yet it has lost some inches at its extremities. These 



